Method of controlling aspirator motive flow

Abstract

Methods and systems are provided for controlling an aspirator shut-off valve in an engine of a hybrid vehicle. One example method includes opening the aspirator shut-off valve following a shut-down command to the engine when engine speed is between a first engine speed and a second engine speed, the first engine speed being lower than an idle speed and the second engine speed occurring before an imminent engine stop. The example method further includes not opening the aspirator shut-off valve between the first engine speed and the second engine speed if an oxygen content of an emission control device is at or near a threshold.

The invention claimed is: 
     
       1. A hybrid vehicle system, comprising:
 an engine; 
 an intake manifold; 
 an intake throttle coupled in an intake passage; 
 a generator coupled to a battery; 
 vehicle wheels propelled using torque from one or more of the engine and the generator; 
 a boost device including a compressor, the compressor positioned in the intake passage upstream of the intake throttle; 
 an ejector coupled in a compressor bypass passage; 
 an ejector control valve (ECV), positioned upstream of the ejector in the compressor bypass passage, regulating motive flow through each of the ejector and the compressor bypass passage; 
 a motive inlet of the ejector coupled to the intake passage downstream of the compressor; 
 a motive outlet of the ejector coupled to the intake passage upstream of the compressor; and 
 a controller with instructions in non-transitory memory and executable by a processor for:
 during a first condition, 
 opening the ECV between a first engine speed and a second engine speed, the first engine speed being lower than the second engine speed; 
 during a second condition, 
 opening the ECV between a third engine speed and a fourth engine speed, the fourth engine speed being nominally higher than that at engine rest; and 
 during a third condition, 
 closing the ECV independent of engine speed. 
 
 
     
     
       2. The hybrid vehicle system of  claim 1 , wherein the first condition includes an engine-on condition for propelling the hybrid vehicle system, the second condition includes an engine shutting down and spinning to rest, and the third condition includes a temperature of the ECV exceeding a temperature threshold. 
     
     
       3. The hybrid vehicle system of  claim 2 , wherein the controller includes further instructions for closing the ECV responsive to one of engine speed being lower than the first engine speed, engine speed being higher than the second engine speed, engine speed being higher than the third engine speed, and engine speed being lower than the fourth engine speed. 
     
     
       4. The hybrid vehicle system of  claim 3 , wherein the first engine speed is based on a transmission lugging limit, the second engine speed is based on a redline speed, and the third engine speed is lower than an idle speed. 
     
     
       5. The hybrid vehicle system of  claim 3 , wherein the temperature of the ECV is based on an amount of heat generated by current flow and an amount of heat dissipated from the ECV. 
     
     
       6. The hybrid vehicle system of  claim 3 , wherein the controller includes further instructions for closing the ECV in response to a pressure in the intake manifold being higher than a pressure at an inlet of the intake throttle.